Elastomer bearings are mechanical elements in which an inner sleeve and an outer sleeve are interconnected adherently by a vulcanized elastomer or rubber layer. These components typically have a cylindrical shape. For adjusting certain mechanical properties, in particular the compliance between the sleeves, the elastomer layer can additionally be provided with intermediate metal sheets or intermediate sleeves.
Cylindrical elastomer bearings serve for damping radial and axial movements, taking up in particular movements which have a twisting effect and cardioid deflections. For this purpose, they are fastened to an associated receiver, for example a bushing, with a force fit or press fit. In this connection, the fit of the elastomer bearing in the receiver is an important quality criterion, this feature being inspected by the pressing-out forces from the receiver being regularly checked under defined conditions and compared with establishing parameters.
For the production of elastomer bearing outer sleeves, use was generally made of tube sections cut off from commercially available precision tube stock. Such tube sections provide the sleeves with great strength and for this reason continue to be used in many cases.
For bearing production, the elastomer is introduced in hot, liquid form into an annular space enclosed by the inner and outer sleeves and vulcanized there. In this connection, owing to material characteristics, the elastomer layer contracts during cooling after vulcanization and removal from the mold. In order to reduce these contraction stresses, the components are calibrated as finished parts. That is to say the outside diameter of the outer sleeve may be reduced, in some cases by several millimeters. This additional operation constitutes a considerable disadvantage, in particular in the case of the tube sections described.
A known development of the sleeves formed from tube sections consists of what are known as “clinched sleeves”, in the case of which it is possible to make the cylindrical sleeve part as a stamping from a plane metal panel, such as a metal sheet. The stamping is bent in a ring shape, so that a ring with a lateral surface which is divided by a slit is produced. The slit is then closed by a positive connection, described as a clinch connection, of the free ends of the stamping. For this purpose, the free ends of the stamping do not have straight edges but complementarily contoured edges, the complementary edge contours engaging in one another to form the connection.
Clinched sleeves are more cost-effective to produce than sleeves consisting of tube sections but have the disadvantage that the strength is markedly lower due to the clinch connection. A further disadvantage is that the connection can be made only partially tight. This is caused in particular by the rubber as a rule being injected in a highly liquid state under high pressure. This in turn results in the rubber as a liquid being able to penetrate through the gaps of the clinch connection, escaping to the outside and solidifying on the outer wall of the sleeve. Consequently, additional cleaning work disadvantageously arises.
Another known development in relation to the sleeves formed from tube sections consists of what are known as slit sleeves. In the case of these sleeves as well, it is possible to produce the cylindrical sleeve part as a stamping from a plane metal panel and then to bend it into a ring. In this case, the slit present in the lateral surface is not closed, the slit sleeves have a defined opening dimension between the free ends of the punching. For assembly, the sleeves are pressed together into a block and inserted into the receiver. As the contraction stresses of the elastomer are then reduced, the elastomer bearing has a firm fit in the support.
Both clinched and slit sleeves belong to the production range of the applicant and are produced from bonding-agent-coated strip.
The object of the present invention is to provide a sleeve, in particular an outer sleeve assembly for an elastomer bearing of the kind referred to in the introduction, which, with high functionality, is characterized by reduced production cost. A further object of the invention consists in providing a corresponding elastomer bearing.
The objects of the invention are achieved for a sleeve of the kind referred to above by virtue of the fact that the sleeve part forms a first, outer sleeve part and is arranged coaxially with a second, inner sleeve part, which both form a slit. The outer sleeve part being, on its inner peripheral surface, and the inner sleeve part being, on its inner peripheral surface and on its outer peripheral surface, provided with a bonding-agent layer, and the slits of the sleeve parts being staggered in relation to one another.
In the outer sleeve assembly according to the invention, neither the inner nor the outer sleeve part is clinched, that is positively connected, but the connection only takes place, specifically by material connection, during the vulcanization of the elastomer, the bonding-agent layers provided according to the invention ensuring the formation of this connection. In this way, an elastomer bearing according to the invention is produced.
It is then also advantageously possible for the connection to be made in a process by the user, and it is realized by the liquid elastomer mixture, in particular rubber mixture, being able to flow between the inner peripheral surface of the outer sleeve part and the outer peripheral surface of the inner sleeve part and in each case to become connected to the bonding agent. Edges which delimit the slits in the outer sleeve part and/or in the inner sleeve part can therefore advantageously be of rectilinear design (i.e. straight cut parallel to the longitudinal axis of the bearing) as they are not intended for forming a connection.
In the production of the material connection between the sleeve parts, provision can advantageously be made, to favor passage of the free-flowing elastomer mixture, that the inner sleeve part comprises openings, in particular at least one slot, preferably two or more slots, extending to the periphery.
The elastomer bearing according to the invention achieves the properties of a tube section with regard to tightness and stability. In this connection, the simpler and therefore more cost-effective production and the novel constructional characteristics described, which also afford opportunities for further structural or assembly-related design possibilities, are advantageous. Calibration of the component elastic stiffness can preferably be dispensed with before the assembly or before the installation of an elastomer bearing according to the invention. In this connection, the sleeve parts are interconnected stably and provide high pressing-out forces.
Defined widths of the slits, which can be provided for the sleeve parts, result in an elastomer bearing according to the invention which, as in the case of use of a slit bushing, has a flexibility which becomes effective advantageously, contraction stresses in the elastomer layer being minimized.
An additional increase in the pressing-out forces can also be achieved, and not only in the case of a sleeve designed according to the invention or an elastomer bearing designed according to the invention, by virtue of the fact that the outer sleeve part is additionally provided on its outer peripheral surface with a bonding-agent layer and an elastomer layer lying over this bonding-agent layer. This results in a dull outer surface which brings about a high coefficient of friction with the associated receiver, which has an advantageous effect on the pressing-out behavior.